1. Field of the Invention
The present invention relates to a caliper of the kind used to measure tree diameters in conjunction with forest inventories.
2. Description of the Related Art
A caliper of that kind includes a fixed scale or graduated rule along which a slide is movable. Provided at one end of the fixed scale and also on the slide are respective legs, wherein measuring is effected between the legs. The measurement is indicated by the position of the slide along the scale or graduated rule. Such calipers are known to the art. Also known to the art are electronic calipers with which said position is indicated electronically and with which the measurement value is presented on a display carried by the slide.
Also known are calipers of that kind that include buttons or keys by means of which the operator can enter data relating to the type of tree concerned, the data being stored in a memory belonging to the caliper, together with actual diameter values.
Such calipers are used in forests under shifting weather conditions. Thus the calipers must be both robust and weather-resistant.
Known calipers have one of two different measuring principles. According to one measuring principle, the graduated rule includes along its length a toothed strip along which a toothed wheel affixed to the slide runs. According to another principle, measuring is effected capacitively between the graduated rule and the slide. That capacitive measuring process is only incremental. It is therefore necessary to first move the slide to a zero position before measuring can take place.
The toothed strip used in accordance with the former principle is easily damaged mechanically. The capacitive principle is sensitive to both moisture and wetness, which can change the capacitance between electrodes on the graduated rule and the slide, respectively.
It is desirable to eliminate those drawbacks.
However, it would be desirable to obtain an electronic caliper that has an absolute measuring function, therewith eliminating the zero setting operation.
The inventive caliper fulfils those desires.